Disabling a search engine pyauto test that's flaky on Mac.

This test appears to fail only when run in the background.

BUG=69619
TEST=search_engines.SearchEnginesTest.testDiscoverSearchEngine
Review URL: http://codereview.chromium.org/7031066

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@86740 0039d316-1c4b-4281-b951-d872f2087c98

chrome/test/functional/PYAUTO_TESTS

@@ -130,6 +130,8 @@
       '-omnibox.OmniboxTest.testHistoryResult',
       # crbug.com/79263
       '-popups.PopupsTest.testPopupsLaunchUponBrowserBackButton',
+      # crbug.com/69619
+      '-search_engines.SearchEnginesTest.testDiscoverSearchEngine',
       # Keychain popups make sync tests difficult on Mac.  crbug.com/49378
       '-sync',
     ],